The private equity firm found NTBY's established brands, long-standing customer relationships and a broad base of distribution appealing, said Sandra Horbach, a Carlyle managing director and head of the its consumer and retail sector team.

In the fiscal second quarter, its net income doubled but fell short of expectations. Revenue rose 18 percent to $705.1 million. The company has a market capitalization — the total dollar market value of all of a company's shares — of about $2.38 billion.

The Carlyle Group has agreed to buy vitamin maker NBTY Inc. for $3.8 billion in cash in one of the largest private equity deals so far this year.NBTY, based in Ronkonkoma, N.Y., makes nutritional supplements and vitamins under the brands Nature's Bounty, Vitamin World and...